Strain-based method for assessment of global resistance safety factors for NLNAs of reinforced concrete structures

This study introduces a novel methodology based on the Global Resistance Format (GRF) for evaluating the design value of the global structural resistance of reinforced concrete (RC) structures. To this aim, an experimental benchmark consisting of 16 RC structural members from the literature has been compiled and the experiments are numerically reproduced through validated non-linear numerical (NLN) modeling assumptions. The tests encompassed various combinations of structural parameters and responses, ranging from brittle to ductile failure modes. The NLN models are used to perform comprehensive probabilistic analyses of the global structural resistance, considering the mechanical uncertainties, to characterize the statistics of the corresponding probabilistic distribution. Then, these statistics have been correlated with the peak strain observed in the primary reinforcement involved in failure mechanism. The peak strain serves as a response indicator representative of the structural failure mode to assess the global safety. The mentioned above correlation allowed to derive predictive expressions that provide the statistical parameters of the global structural resistance as a function of the peak strain in the primary reinforcement. This latter one is computed through a single NLN analysis performed with the mean values of mechanical properties and nominal geometrical ones. In this way, the statistics, so far estimated, can be directly employed to determine the design value of the global structural resistance according to the target reliability levels for both new and existing RC structures. Finally, the achieved results have been compared with those of other established safety formats within the GRF confirming the effectiveness of the proposals.